Conventionally, an FDD wireless communication system using different frequencies for transmission and reception and a TDD wireless communication system using the same frequency for transmission and reception have been practically used.
In order to effectively use frequencies, in a frequency band of quasi-millimeter or higher waves, the FDD wireless communication system and the TDD wireless communication system are used in close frequency bands. However, in the conventional techniques, the coexistence of a TDD wireless device associated with the TDD wireless communication system and an FDD wireless device associated with the FDD wireless communication system is difficult to be realized due to the difference in filter configurations between an antenna and the wireless devices.
This is because the TDD wireless device has the filter pass characteristic that the transmission frequency and the reception frequency are the same while the FDD wireless device has the filter pass characteristic that the transmission frequency and the reception frequency are different from each other so that a duplexer is utilized to branch and separate the frequencies. Even assuming that a common TDD/FDD wireless device is realized, RF line routing would be complicated and RF switches would be used extensively to avoid the provision of the duplexers, increasing power consumption or degrading reception characteristics. Therefore, it is necessary to sacrifice any one of the wireless communication systems.
As described above, it is difficult to provide a single wireless device compatible with both FDD and TDD wireless communication systems, and the wireless device has been scaled up and become more expensive since the wireless device is to be installed in each system even though the baseband unit can be shared.
For the above reasons, in practical use, separate wireless devices have been used in the TDD wireless communication system and the FDD wireless communication system.
As an example of the conventional techniques relating to a common device used for both a FDD scheme and a TDD scheme, there has been proposed a distortion compensation device that is compatible with both the FDD scheme and the TDD scheme and implements a delay adjustment precisely reflecting an effective data period (see, e.g., Patent Document 1).
Patent Document 1: Japanese Patent Application Publication No. 2013-58910